Magnetoresistive devices change their electrical resistance in the presence of a magnetic field. Anisotropic Magneto Resistive (AMR) sensors include a material in which there is a dependence of its electrical resistance on the angle between the direction of electric current and the direction of magnetization observed. AMR sensors offer robust non-contact measurement of changes in the magnetic field as seen by the sensor, where the AMR sensor can detect the presence, the strength, and/or the direction of the magnetic field. The strength of the magnetic field may be represented by a magnitude and a polarity (positive or negative). The direction of the magnetic field may be also described by its angular position with respect to the AMR sensor.
In typical applications for AMR sensors, magnetoresistive materials such as nickel iron (NiFe) having top electrical connections are used to detect the component of a magnetic field that lies in the plane of the MR material. In some applications, the MR material is disposed in a serpentine array on the surface of a substrate such as silicon. The serpentine pattern of MR material can be electrically connected in a Wheatstone bridge arrangement (4 resistors) or a pair of Wheatstone bridges in order to sense changes in the resistance of the MR material in response to changes in the strength of a magnetic field component in the plane of the MR elements. In order to monitor the changes in the resistance of the MR material, associated components such as amplifiers are generally connected together to form an electrical circuit which provides an output signal that is representative of the strength of the magnetic field in the plane of the MR sensing elements.